The murder case of a young woman whose body has not been found hinges upon a "large and complex" body of circumstantial evidence, a Toronto judge said Thursday as he instructed the jury.

Laura Babcock, a troubled 23-year-old Toronto woman, vanished five years ago.

Two men -- Dellen Millard and Mark Smich -- are accused of killing Babcock in July 2012 and burning her body in an animal incinerator.

Justice Michael Code told jurors the circumstantial evidence focuses on two main issues: whether Babcock is dead and whether Millard and Smich caused her death from an unlawful act.

Those are two key elements of murder, he said.

"Facts may be proved by circumstantial evidence," Code said. "It is all about inference drawing. You observe some fact and from that fact you draw an inference or conclusion."

The prosecution alleges Babcock was killed because she was the odd woman out in a love triangle with Millard and his girlfriend, Christina Noudga.

Millard, 32, of Toronto and Smich, 30, of Oakville, Ont., have pleaded not guilty to the first-degree murder charges and both have said the Crown has not proved that Babcock is dead.

The judge hammered home the point multiple times that circumstantial evidence must be looked at in totality, not each piece of evidence in isolation.

He summarized seven key points of circumstantial evidence that came up throughout the seven-week trial: motive, opportunity, evidence of the incinerator and Millard's handgun purchase, Babcock's disappearance, her risky lifestyle, the use of the incinerator on July 23, 2012, and statements made by Millard and Smich after the Toronto woman disappeared.

The judge quickly went through the evidence that came up during the trial and expects to go through it thoroughly again on Friday.

He noted the cellphone data that puts Millard's phone in the same area as Babcock's phone around 6:30 p.m. on July 3, 2012, both phones travelling to Millard's home where Smich's phone was located.

Babcock's last outgoing phone call occurred at 7:03 p.m. and her phone stopped connecting with cell towers at 11:11 a.m. on July 4.

"Her friends and her family have never seen her again or heard from her again and they have never been able to contact her," the judge said.

"These are critical pieces of evidence."

He also noted the handgun Millard bought on July 2, although he said there is no evidence Millard had ammunition for that gun, and Babcock's iPad and bag that were found at Smich's home. He noted her transient lifestyle, living as an escort, her struggles with her mental health and cocaine use.

He spoke at length about the incinerator, named The Eliminator, that Millard bought for $15,000 and outfitted it on a trailer for about another $10,000. The pair dubbed the machine "the BBQ."

Code also spoke about a photo of a smiling Smich in front of the incinerator.

"I'm simply trying to make the point that there is a relatively large and complex body of circumstantial evidence and you must assess it in its totality," Code said.

In its closing address on Wednesday, the Crown said a "mountain" of circumstantial evidence points to Millard and Smich killing Babcock at Millard's home some time after 8 p.m. on July 3, 2012, and then disposing of her body at Millard's farm near Waterloo, Ont.

Smich's lawyer told the jury on Wednesday that his client had no motive to kill Babcock because he was never part of a love triangle and all the Crown has is a rap song in which Smich says he killed a girl and burned her body.

The judge noted in his instruction that the Crown doesn't need to prove motive as part of proving its case.

"Motive is simply a piece of evidence," Code said.

Millard, who is representing himself, told the jury in his closing address earlier this week that several witnesses testified to having seen or heard from Babcock after July 4, 2012.

The judge told the jury his 300-page instruction will last multiple days before they can begin deliberating.